“Sam and Lindsay are speaking,” the source tells PEOPLE. “But Sam has begged Lindsay to get help.”

“Lindsay, despite appearances, is insecure and has relied on Samantha and their relationship to build her up,” explains the pal. “Lindsay barely sleeps, which explains a lot of her behavior. She’s exhausted. She can’t even sit down for a minute without pacing around the room. It’s really sad.”

Since Ronson broke up with her last week in Los Angeles, Lohan has kept busy: Thursday night, she was spotted at the Chateau Marmont before meeting up with friends at Bar Delux, where a fellow club-goer reported, “her mood was frantic. She looked worn out, and really skinny.” A source also tells PEOPLE that “Lindsay continued partying after Delux that night.” Friday night Lohan laid low while Ronson deejayed a party in San Francisco.

Lohan’s tendencies for erratic behavior have sparked concern among Ronson’s friends that Lohan might act out, but her friend says that she is not the only one to blame for the former couple’s intense dynamic.

“While Sam doesn t want to deal with the drama, in a sick way she is obsessed with this part of Lindsay’s behavior,” the friend says. “It’s like she doesn’t want it, but when Lindsay stops writing, she begins to miss it.”

Despite her difficult week, Lohan has discovered a silver lining in the support she’s received from her younger sister Ali. “Lindsay never realized until this happened how important her sister was to her,” the friend says.

“Through all of this, her sister has been there for her and coaching her through it. Lindsay doesn’t even know what she would have done without her.”